a ready market. The poor people use the crude oil, which they purchase at 

 half the price of the refined. There was no evidence of any other useful 

 minerals in this district. The coal-beds however must be very extensive and 

 valuable. 



Working southward from Yen-an Fu, the same horizontal sandstone bed- 

 rock without faults is encountered, whilst the loess deposits are in the form of 

 great plateaux, all uniform in height (Plate 22). These continue from Fu 

 Chou to near Chung-pu Hsien, a distance of about seventy miles. South of 

 the latter town the rock-beds, in the form of shale, rise considerably above 

 their normal level, and the loess mantle is very much reduced in thickness, 

 being in some places entirely denuded. Continuing southward, we found the 

 shale strata very much contorted. Still further south again, at Yao Chou, we 

 passed through a great outcrop of grey limestone, dipping sharply to the north. 

 This seems to mark the southern boundary of the great North Shensi basin. 



From here the coQntry gradually slopes down to the Hsi-an plain. The 

 loess on the southern side of the limestone ridge is very thick, completely 

 hiding the under-lying rock, and extending right over the plain. The country 

 south of the Wei Ho was visited by the Carnegie Expedition, and a good 

 account of its geology appears in the book subsequently published by the 

 Carnegie Institution. I will not do more than draw attention to the variable 

 temperature of the hot springs at Lin-t'ung Hsien. Bailey Willis found 

 them to be 40° Centigrade (104° F.). Kockhill records their temperature at 

 106° F. When we visited them they were at 108° F. whilst Dr. Jenkins, a 

 resident missionary of Hsi-an Fu says that he has known them to reach 

 112° F. In the mountains immediately south of Hsi-an Fu I found granite 

 occuring at very low levels. Viewing the mountains southward from the 

 top of the peak, about 5000 feet in altitude, I could make out nothing but 

 igneous rock masses. 



Leaving this vicinity we will now follow the westward course of the main 

 division of our Expedition on its way to Lan-chou Fu in Kansu, and for this 

 we must return to Fu Chou. From that point westwards for about thirty-four 

 miles the same loess plateaux as lie to the south and east were encountered. 

 Then a stretch of very moist country : deep and clear streams in every valley 

 and ravine : the hills clothed with luxuriant vegetation. Denudation must have 

 been at one time very extensive, for not only is the loess low and well rounded- 

 off, but the sandstone and shale substrata also show marked wearing. 



At Hai-shui-ssu, a peculiar column of sandstone — all that is left of a 



124 



